In recent years the rapid expansion of the world's population coupled with the accelerated technological development of large sectors of the world has produced a dramatic increase in the demand for energy in all forms including fuels and electricity for heating, lighting, transportation and manufacturing processes. The construction of hydroelectric facilities and the development of fossil fuel resources has continued at a rapid rate, but it becomes increasingly evident for a number of reasons that these efforts are inadequate to keep pace with the demands of the growing population.
In the face of these growing demands and limited resources, there is one source of energy which is readily available to every country in the world in virtually unlimited quantities. This untapped source is solar energy. The World Book Encyclopedia (copyright 1963, U.S.) states that the amount of solar energy reaching the earth in one day equals the energy that could be produced by burning 550,000, 000,000 tons of coal, i.e., as much coal as would be dug in the United States in 1,000 years at the 1963 rate of mining. It further states that enough solar energy reaches the United States in 20 minutes to fill the country's entire power needs for one year.
The interest in this almost boundless resource and in its development and harnessing for use in homes and factories is rising as other resources dwindle. Its desireability is further enhanced by the fact that solar energy may be converted to practical use without the hazard of environmental contamination.
Apart from such important considerations as energy conservation and environmental concerns, solar power has other advantages to offer for special applications such as the control of remotely positioned irrigation systems, advertising sign displays and the like.
Irrigation systems are frequently installed in relatively remote locations where electric power at secondary voltages is not immediately available. Locations in this category include new housing development entries, highway medians, parks, golf courses, orchards and all types of landscaped areas. In such applications, solar power units permit fast and simple installations. There is no requirement for immediate utility line extensions with the attendant costs and inconvenience. The advantages continue after installation in the form of reduced operating costs. There are no utility bills to be paid. In addition, the absence of high voltages in the power unit significantly reduces safety hazards for service personnel or uninvited intruders. This is an especially important consideration in remote locations.